A firefighter stands close to the remains of a train wreckage in Lac Megantic July 8, 2013.Mathieu Belanger

OTTAWA (Reuters) - Canadian investigators probing a train disaster that killed 47 people in Lac-Megantic, Quebec, urged U.S. and Canadian regulators on Wednesday to review the processes for transporting or importing dangerous goods to ensure proper documentation.

The Transportation Safety Board (TSB), which does not have the power to impose changes, said in a release that test results showed the crude being transported in tank cars that crashed into Lac-Megantic were not accurately documented and had a lower flash point, explaining in part why it ignited so quickly.

Changes in crude labeling could have implications for the rising volumes of crude-by-rail shipments across North America, which has gained in popularity as pipelines fill to capacity.

"The TSB identified the product as having the characteristics of a Dangerous Good of Class 3, PG II product. However, the product was offered for transport, packaged, and transported as a Class 3, PG III product, which represented it as a lower hazard, less volatile flammable liquid," the agency said in a statement.

"The lower flash point of the crude oil explains in part why it ignited so quickly once the Class 111 tank cars were breached."

The train, hauling 72 tanker cars of Bakken crude, was parked uphill of the Quebec town of Lac-Megantic when it rolled away, accelerated on a downhill grade and derailed and exploded in vast fireballs in the center of town.

The fireballs had already raised concern about the cargo, given that crude oil does not normally explode very readily. Bakken crude is lighter, and hence more volatile, than crude from some other areas.

The TSB has already said trains carrying dangerous goods must not be left unattended on a main track, and two "qualified persons" must run any train that hauls dangerous goods.

The train in the Lac-Megantic crash, operated by now-bankrupt railroad Montreal Maine & Atlantic, had a single engineer aboard when it was parked for the night on the main line.